1. Field of the Invention
The present invention is directed to a method and apparatus for determining the location of perforations and, more particularly, to measuring the location of film during film to video conversion in a continuous motion telecine, so that mechanical or electronic means can be used to correct for undesirable motion.
2. Description of the Related Art
A number of techniques to reduce image unsteadiness in video converted motion picture film have been attempted. U.S. Pat. Nos. 4,823,204, 4,104,680 and 4,296,438 cover a variety of aspects of film motion detection using a flying spot scanner. U.S. Pat. Nos. 4,296,438 and 4,875,102 use charge coupled device sensors to accomplish the same result. Other techniques, typified by U.S. Pat. Nos. 4,864,149 and 4,319,280 use the film frame and light sensors to detect the characteristics of the passing film. Still other techniques as typified by U.S. Pat. Nos. 4,207,473 and 4,578,483 detect the film edge or marks along the edge of the film. In addition, techniques for detecting marks on and edges of webs exist such as described in U.S. Pat. Nos. 4,857,745 and 4,146,797. These patents share, in common, a scanning input of some type to perform the detection of motion. Of these techniques some are very complex and would be unsuitable for real time operation and others are not capable of detecting the center of a perforation, the edges of a perforation and the lateral displacement of the perforation while adjusting the illumination level of a detector light source to produce consistent signals suitable for perforation detection during film to video conversion.